Japanese Patent Laid-Open No. 2008-125523 discloses coating the outer surface of a medical body with a fluororesin for obtaining enhanced sliding properties. The fluororesin can normally be fixed onto the outer surface of a substrate member of a guide wire by burning the resin at a temperature (350 to 400° C.) not lower than its melting point. In carrying out a fluororesin burning treatment by an existing circulating hot air oven, the intended uses may include drying a medical body (work), fixation of a resin or other coating onto a metal, and extension or straightening of a medical body by heat.
It has been believed that burning a fluororesin by an existing circulating hot air oven makes it difficult to protect a metallic substrate wire inside a medical body from thermal energy (see, for example, Japanese Patent Laid-Open Nos. 2008-86575 and 2006-320638). Specifically, it has been believed that if temperature is raised to the melting point of the fluororesin, the characteristic properties of the metallic substrate being coated with the fluororesin would be spoiled or lost. For example, where the metallic substrate of the medical body is composed of a superelastic alloy, it has been thought that the superelasticity of the superelastic alloy wire is lost by such heating. In addition, the use of an existing circulating hot air oven may involve a number of other problems such as summarized below.
In one respect, the number of works that can be placed in the oven is limited, and the flow of hot air leads to swinging of the works and eventually to mutual contact of the works or dropping of the works.
Opening/closing of the oven door causes a temperature fall, and the starting temperature varies or is scattered according to the door-open time, so that the treating conditions vary.
Additionally, setting the work(s) is troublesome, and in situations where the treatment is repeated a number of times, especially, in the case where the work is long, other storage space(s) is needed, and the cooling time during when the work(s) is placed outside the oven varies or is scattered.
The openable door is so large that a human can enter the oven, which is dangerous.
Also, notwithstanding the forced circulation, the temperature rise gradient at the rise time is gentle, and thermal efficiency is often low, so that much energy is consumed in warming up the apparatus itself.
Further, where the work is relatively large or long, the apparatus must also be relative large in size and high in cost.